Nice primes: Difference between revisions

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 :983  dr(2)
 :997  dr(7)
+</pre>
+=={{header|C++}}==
+<lang cpp>#include <iostream>
+bool is_prime(unsigned int n) {
+    if (n < 2)
+        return false;
+    if (n % 2 == 0)
+        return n == 2;
+    if (n % 3 == 0)
+        return n == 3;
+    for (unsigned int p = 5; p * p <= n; p += 4) {
+        if (n % p == 0)
+            return false;
+        p += 2;
+        if (n % p == 0)
+            return false;
+    }
+    return true;
+}
+unsigned int digital_root(unsigned int n) {
+    return n == 0 ? 0 : 1 + (n - 1) % 9;
+}
+int main() {
+    std::cout << "Nice primes between 500 and 1000:\n";
+    for (unsigned int n = 501; n < 1000; n += 2) {
+        if (is_prime(n) && is_prime(digital_root(n)))
+            std::cout << n << '\n';
+    }
+}</lang>
+{{out}}
+<pre>
+Nice primes between 500 and 1000:
 </pre>